DescriptionBlythophryne beryet is a small, robust toad. The adult females have a snout-vent range between 25 – 27 mm and the adult males are between 22 – 25 mm long. The head is almost as long as it is wide and without cephalic ridges. The snout is blunt from the dorsal viewpoint and projects beyond the mandibles. The laterally oriented nostrils sit on the lateral fold closer to the tip of the snout than to the eye. The loreal region is slightly concave with a well-defined canthal ridge between the nostril and the eye. The distance between the orbit and nostril is greater than internarial distance. The upper eyelid is rough and covered with small warts. They have large eyes that are about twice the length of the tympanum and are separated by twice the internarial distance and over twice the width of the upper eyelid. There is no pineal ocellus. The parotoid glands are elongated and slender, next to a well-defined postorbital ridge (Chandramouli et al. 2016).

With slender limbs, B. beryet has short upper arms and longer lower arms. Their fingers are webbed toward the base with the webbing between fingers 2 and 3 not exceeding the penultimate subarticular tubercle. They have a webbing formula of I0-1II1-2III2-1IV for their fingers. At the palmar base there are enlarged, prominent outer metacarpal tubercles. Males did not have nuptial pads. Subarticular tubercles are prominent on fingers and toes. The fingertips are wider than they are long, are dilated into discs and lack circummarginal grooves. The discs are less visible in the first and second fingers. The fingers have a relative length of 3 > 4 > 2 > 1. The toes are partially webbed, the webbing goes from toes 3 and 4 to the second to last subarticular tubercle and the webbing formula is I0-1II0-1III1-2IV21⁄2-1⁄2V. The tarsal ridge is absent and the inner meta-tarsal tubercle is larger than the outer tubercle. The relative toe lengths are 4 > 5 > 3 > 2 >1 (Chandramouli et al. 2016).

Dorsally, the skin is rough while ventrally it is granular. The dorsolateral fold is easily noticeable. The lower abdomen has a loose skin flap. Tubercles and granules are absent on dorsum but are scattered over the venter. The surface under the thighs are less granular. The throat and limb insertions are covered with dense granules. The tibia has enlarged granular tubercles (Chandramouli et al. 2016).

At stage 20 tadpoles had dorsally positioned eyes and visible labia. At stages 30 and 35 the tadpole larvae, have no dorsal pattern. Stages 41 and 43 had tadpole metamorphs with developed forelimbs, expanded disc of fingers, and a slight barred pattern on the limbs. The mouth is anteriorly located with a prominent keratinized pair of jaw sheaths during stage 43. The eyes and nostrils pointed dorsolaterally with the nostrils closer to the eyes than the snout tip. The body is depressed and the tail is almost twice as long as the broad head-body. The distance between the two orbits from stage 30 to stage 43 was about 1/5 the body length, while the distance between the external nares was about 15% the body length. During stages 30 to 43 the distance between the nostril and eyes changed from 8% to 11% the body length. While the distance from the snout to the eye was about 14% the body length. At stage 30 the spiracle is about 3/4ths the body length. The snout to vent is about 1/3 the body length around stage 30 and increases to ½ at stage 35. Distance from snout tip to point of the start of tail from the body grew about 71% whereas distance from start of tail to tip of tail remains about ½ the body length. The tadpole’s maximum body width ranged from 2.8 mm to 3.8 mm across stages 30 to 41. Laterally, the maximum height of the tail shrunk from ½ the body length to about ¼ near stage 43. While the distance from the start of the tail to its maximum width shrank from 22% to about 17% . There is an increase in the distance from the start of the tail to where the muscle width is at its maximum height. The oral disc diameter remained about ¼ the body length while the vent tube length went from 1/7 the body length to being non- existent on the tadpole. The vent fin height shrinks from 0.4 mm to 0.3 mm (Chandramouli et al. 2016).

More specifically, when tadpoles of Blythophryne beryet are at stage 35, they are endotrophic larvae, have a tubular body when viewed dorsally and an ovoid body when viewed laterally. Ventrally the body is slightly flattened at the anterior end and convex toward the posterior. The body reaches its maximum diameter immediately behind the eyes. The snout is broad but truncate when dorsally viewed and pointed when viewed laterally. Their large eyes are oriented and located dorso-laterally. Rounded nostrils with an elevated rim are located about midway between the eyes and snout, a little closer to the eyes, and linear to the eye when viewed dorsally. The internarial distance is subequal to the interorbital distance. There is no inner wall on the long sinistral spiracle; the spiracle opening is large. The tube is oriented postero-laterally and the opening is approximately at mid body. The distance between the spiracle and the snout is about sixty percent of the body length. The tip of the tail is broadly rounded and the musculature is linear until about one-third the length of the tail, after that it tapers off. The dorsal fin, which is posteriorly orientated, is slightly wider than the ventral fin. The tail junction and ventral fin meet at the ventral terminus. Both of the fins run parallel to the tail muscle and remain parallel through the entire length of the tail. The tail reaches maximum height at about mid-length. The lateral line is faintly visible and there are no glands observed on the outer integument. At the terminal portion of the body, the oral disc opens antero-ventrally. The entire oral disc is visible dorsally. There is a single row of seven to eight large marginal papillae on the lower labium and two or three on the lateral corner, there are none present on the upper labium. However, there is a single submarginal papilla located at each lateral corner. The lower labium is larger than the upper one. There are no denticle rows. The jaw sheath is well developed and heavily keratinized. Jaw sheaths are completely serrated with more minute serrations on the lower jaw than on the upper jaw (Chandramouli et al. 2016).

Blythophryne beryet is different from other bufonid genera because of its small adult size. The Andaman bush toad differs from Parapelophryne scalpta due to the presence of six prescaral vertebrae in the former versus the eight present in the latter. Blythophryne beryet also has an elongated pair of parotoid glands and expanded discs at their digit tips whereas Pedostibes tuberculosus has shorter, rounded paratoid glands and tips of fingers that are dilated into truncated discs. While Pelophryne albotaeniata has coccygeal expansions B. beryet does not have coccygeal expansions (Chandramouli et al. 2016).

In life, adult Blythophryne beryet has a reddish-brown dorsum with two faint dark brown inverted ‘V’ shaped markings that do not fully reach the flanks. The interorbital band is indistinct. The canthus is a dark chocolate brown and this brown extend a little beyond the tympanum. The forearms and hindimbs are barred and one stripe is on each thigh, shank, and tarsus. The venter is heavily speckled with dark brown spots, while the throat is a solid dark brown. The lower lip is spotted white and brown. In preservative, the dorsum is a drab brown with indistinct “inverted-V” shaped patterns. There are darker bands on the limbs and the venter is cream colored with a black mottled pattern. The throat is black (Chandramouli et al. 2016).

In life, the dorsal side of the Blythophryne beryet tadpoles’ outer integument is brown with no melanopores. At stage 20 they were colorless and at stages 30 - 35 they remained dull in color. Around stages 41 and 43 they had more pigmented skin. Ventrally the integument is translucent however the gut was not visible. The throat is speckled. Both tail fins are transparent with few melanophore. Laterally the tail muscle is white with a few brown spots spread mainly at the anterior region of the tail (Chandramouli et al. 2016).

In life, a completely transformed metamorph resembles an adult with the inverted ‘V’ on the dorsum and the dark bands on the limbs (Chandramouli et al. 2016).

Blythophryne beryet has been found on five islands of the Andaman archipelago: South Andaman, Ruthland, Little Andaman, Havelock Island in the Ritchie’s Archipelago and North Andaman. It can often be seen, year round, on the surface of herbaceous bushes at night or on the forest floor during the day. They are found on the islands from 29 - 250 m above sea level and are the most common above 100 m above sea level. The forests in this range include littoral, moist-deciduous, giant evergreen and montane stunted evergreen forests (Chandramouli et al. 2016).

Life History, Abundance, Activity, and Special Behaviors

Blythophryne beryet are nocturnal and occupy the leaves of herbaceous bushes when active. During the day they can be found under leaf litter on the forest floor (Chandramouli et al. 2016).

The Andaman bush toad can release a toxic white, pungent smelling secretion from the parotid gland. This secretion has been seen while the species was being handle. When placed with other species of frogs while they have this white secretion, the other frogs have died. This toxin is presumed to be related to predation avoidance (Chandramouli et al. 2016).

Breeding occurs in June before the Southwest Monsoon. Males will call from perches on leaves of bushes about 1 - 1.5 m above the ground. A male toad was observed making a mating call on the surface of leaves among the bushes on 24 November 2010. The calls consisted of “pip-pip-pip-pip-pip-”at a constant frequency of 8 kHz, with no break and lasting 23 seconds. They have a mean amplitude of -3db/ 20 kU. The call consisted of 198 pulses within 23 s, at a rate of 8 to 9 pulses per second, with each pulse lasting from 0.3 s with an interval of 8.5 s between two consecutive pulses (Chandramouli et al. 2016).

Females deposit ova in tree-holes that are filled with rainwater at about the same height that males call from (1 - 1.5 m). The tadpoles develop in these phytotelms, tree-holes. A clutch of eggs was observed continuously and it was found that the tadpoles can be washed out of the phytotelm by rain overflow (Chandramouli et al. 2016).

Trends and Threats

A wide variety of invasive fauna on the islands and anthropogenic pressures, threaten the bush toad and has made them endangered. Additionally, because of low densities, the species is sensitive to random events. Given its small, fragmented range, and because it is known from few localities, it is recommended to be listed on the IUCN Red list as “Endangered” (Chandramouli et al. 2016).

Possible reasons for amphibian decline

Predators (natural or introduced)Introduced competitors

Comments

The species authority is: Chandramouli et al. (2016). "A new genus and species of arboreal toad with phytotelmonous larvae, from the Andaman Islands, India (Lissamphibia, Anura, Bufonidae)." Zookeys 555, 57-90.

In an analysis of 36 species from 21 genera, Blythophryne beryet was revealed to be most closely related to Bufoides meghalayanus using maximum likelihood analysis from concatenated partial 12S and 16S rDNA sequences. However, better sampling of more species will likely change this result (Chandramouli et al. 2016).

Blythophryne beryet is the third most common frog on the islands because its unique niche and narrow range of distribution (Chandramouli et al. 2016).

It is believed that the family, Bufonidae, is South American origin and rapidly dispersed across the world. Eventually they returned to South America, however bits of their lineage are still unclear (Chandramouli et al. 2016).